Coherent potential approximation

About: Coherent potential approximation is a research topic. Over the lifetime, 1930 publications have been published within this topic receiving 36805 citations.

The effects of short-range order and natural microinhomogeneities on the FIR optical properties of Cd x Hg 1−x Te

Abstract: Possible types and formation mechanisms for the correlated cation distributions in CdxHg1−xTe alloys, including short-range order (SRO) in the mixed sublattice and composition microinhomogeneities (MI), are discussed. The impact of SRO (ordering or clustering) on phonons is studied in the framework of the coherent potential approximation. It is shown that two peaks of the spectral density of phonon states with $$\overrightarrow q $$ =0 (HgTe-like and CdTe-like modes) move toward and away from their positions in end member crystals due to clustering and ordering, respectively. Short-range ordering also activates (HgTe-like and CdTe-like states of the Brillouin zone edge, but this effect is small. The effects of composition MI on the dielectric response due to phonons are considered and an effective dielectric function is calculated using the modified Maxwell-Garnett approach. It is shown that separate inclusions of different composition produce extra modes of the Frohlich type in FIR spectra of CdxHg1−x Te. It is argued that this is a more plausible explanation of the experimenatally observed ‘cluster’ mode (133 cm−1 in Raman and 135 cm−1 in FIR spectra) than one which previously appeared in the literature and involves atomic ordering in the mixed sublattice.

Charge transport and metal–insulator transition in correlated and disordered systems

Abstract: The metal-insulator transition induced by sufficiently strong short range repulsive electron-electron interaction U is called Mott-Hubbard transition. In this work we study the effect of disorder on the critical value of the repulsion U c . The Hubbard model with random site energies to describe the correlated and disordered system has been used. The Kotliar-Ruckenstein slave-boson technique to treat correlations and coherent potential approximation (CPA) to deal with disorder have been applied. We have found that the low temperature conductivity is an increasing or decreasing function of U depending on the carrier concentration. The critical value U c for metal-insulator transition is decreasing function of the disorder strength.

Two band model of a disordered semiconducting binary alloy in the coherent potential approximation

Abstract: Formalism of the coherent potential approximation is extended to include the two band case. Single site energy of the one band case is replaced by a 2 × 2 matrix which varies randomly from site to site according to the occupancy of the site. Cases treated explicitly correspond to fully disordered binary alloys. Band gap and band widths are chosen as representative of typical semiconductor values. Concentrations, band gaps, gap centers, and band mixing are all varied systematically. Results are exhibited for the total densities of states and their parentage. Various limits of splitband and gap closure are shown by phase diagrams.

Electronic structure of the disordered‐local‐moment state of face‐centered‐cubic iron

Abstract: We calculate the electronic structure of fcc iron in the disordered‐local‐moment state using the self‐consistent Korringa–Kohn–Rostoker coherent‐potential approximation (KKR‐CPA). As the volume is reduced the moments decrease and, as many previous calculations have shown, there is also a change from ferromagnetic to antiferromagnetic correlations between local moments. In this paper, we show that there is a corresponding change from split to common band behavior of the electronic states and suggest that this is important in understanding the changing nature of magnetic interactions.